Immersion upper layer film forming composition and method of forming photoresist pattern

ABSTRACT

An immersion upper layer film composition includes a resin and a solvent. The resin forms a water-stable film during irradiation and is dissolved in a subsequent developer. The solvent contains a monovalent alcohol having 6 or less carbon atoms. The composition is to be applied to form a coat on a photoresist film in an immersion exposure process in which the photoresist film is irradiated through water provided between a lens and the photoresist film.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application of the U.S. patentapplication Ser. No. 10/586,187, which in turn is a national stageapplication of International Application No. PCT/JP2005/000346, filedJan. 14, 2005, which claims priority to Japanese Patent Application No.2004-008466, filed Jan. 15, 2004,to Japanese Patent Application No.2004-185706, filed Jun. 24, 2004, and to Japanese Patent Application No.2004-233463, filed Aug. 10, 2004. The contents of these applications areincorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an immersion upper layer filmcomposition and a method of forming photoresist pattern.

2. Discussion of the Background

In the manufacture of semiconductor devices and the like, a stepping orstep-and-scan projection exposure device (aligner) has been used inwhich a pattern of a reticle (photomask) is transferred onto each shotregion on a wafer provided with a photoresist through a projectionoptical system.

The resolution of the projection optical system provided in theprojection exposure device increases as the exposure wavelength usedbecomes shorter and the numerical aperture of the projection opticalsystem becomes greater. Therefore, the exposure wavelength which is thewavelength of radiation used in the projection exposure device has beenreduced along with scaling down of integrated circuits, and thenumerical aperture of the projection optical system has been increased.

The depth of focus is also important for exposure in addition to theresolution. The resolution R and the depth of focus δ are respectivelyshown by the following expressions.R=k1·λ/NA  (i)δ=k2·λ/NA²  (ii)

In the above expressions, λ is the exposure wavelength, NA is thenumerical aperture of the projection optical system, and k1 and k2 areprocess coefficients. When obtaining the same resolution R, a largerdepth of focus λ is obtained by using radiation with a shorterwavelength.

In the above case, a photoresist film is formed on the surface of theexposure target wafer, and the pattern is transferred to the photoresistfilm. In a related-art projection exposure device, the space in whichthe wafer is placed is filled with air or nitrogen. When the spacebetween the wafer and the lens of the projection exposure device isfilled with a medium having a refractive index of n, the resolution Rand the depth of focus δ are shown by the following expressions.R=k1·(λ/n)/NA  (iii)δ=k2·nλ/NA²  (iv)

For example, when using water as the above medium in the ArF process,since water has a refractive index n for light with a wavelength of 193nm of 1.44, the resolution R is 69.4% (R=k1·(λ/1.44)/NA) and the depthof focus is 144% (δ=k2·1.44λ/NA²) of the values during exposure usingair or nitrogen as the medium.

The above projection exposure method in which the wavelength of exposureradiation is reduced to transfer a more minute pattern is called animmersion exposure method. The immersion exposure method is consideredto be an essential technology for lithography with reduced dimensions,particularly for lithography with dimensions of several ten nanometers(Japanese Patent Application Laid-open No. 11-176727).

In the immersion exposure method, both the photoresist film to beapplied and to be formed on a wafer and the lens of the projectionexposure device respectively contact with water. Therefore, water maypermeate the photoresist film, whereby the resolution may be decreased.Moreover, the photoresist components may be eluted (dissolved) in water,thereby causing contamination of the lens surface of the projectionoptical system.

An upper layer film may be formed on the photoresist film in order toprotect the photoresist film from water. The upper layer film whichexhibits sufficient transparency for the exposure wavelength, can form aprotective film on the photoresist film without being intermixed withthe photoresist film, is not eluted into water during immersion exposureto maintain a stable film, and is easily dissolved in an alkalinesolution as a developer are demanded.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, an immersion upperlayer film composition includes a resin and a solvent. The resin forms awater-stable film during irradiation and is dissolved in a subsequentdeveloper. The solvent contains a monovalent alcohol having 6 or lesscarbon atoms. The composition is to be applied to form a coat on aphotoresist film in an immersion exposure process in which thephotoresist film is irradiated through water provided between a lens andthe photoresist film.

According to another aspect of the present invention, a method offorming a photoresist pattern includes providing a photoresist on asubstrate to form a photoresist film. The immersion upper layer filmcomposition is provided on the photoresist film to form an upper layer.The photoresist film and the upper layer are exposed with radiationthrough a predetermined mask pattern and through water. The photoresistfilm and the upper layer are developed to form a resist pattern.

DESCRIPTION OF THE EMBODIMENT

An embodiment of the present invention provides an immersion upper layerfilm composition applied to coat on a photoresist film when using animmersion exposure device which is irradiated through water providedbetween a lens and the photoresist film, and the composition comprises aresin forming a water-stable film during irradiation and being dissolvedin a subsequent developer, and a solvent containing a monovalent alcoholhaving 6 or less carbon atoms.

The resin comprises a recurring unit having a fluorine atom-containinggroup on the side chain.

The recurring unit having a fluorine atom-containing group on the sidechain is the recurring unit having an alcoholic hydroxyl group on theside chain containing the fluoroalkyl group on at least the carbon atomof α-position.

The recurring unit having an alcoholic hydroxyl group on the side chaincontaining the fluoroalkyl group on at least the carbon atom ofα-position comprises a recurring unit of the following formula (1).

In the formula (1), R¹ represents a hydrogen atom or a methyl group, andR² represents an organic group.

An embodiment of the present invention also provides a method to form aphotoresist pattern comprises the steps of forming a photoresist film byapplying the photoresist on a substrate, forming an upper layer film onthe photoresist film by using the immersion upper layer filmcomposition, and forming a resist pattern by exposure with radiationthrough a predetermined mask pattern with water and development.

The embodiment of the present invention provides an immersion upperlayer film composition to form the upper layer film which exhibitssufficient transparency for the exposure wavelength, particularly for aKrF excimer laser (wavelength: 248 nm) and an ArF excimer laser(wavelength: 193 nm), can form a protective film on the photoresistwithout being intermixed with the photoresist film, is not eluted intowater used during immersion exposure to maintain a stable film, and canbe easily dissolved in an alkaline developer.

Since the immersion upper layer film composition to form the upper layerfilm according to the embodiment of the present invention can be easilyapplied to a photoresist film, the upper layer film protects a lens andthe photoresist film during immersion exposure, and can form a resistpattern with an excellent resolution, developability, and the like.Therefore, the composition is extremely useful in the manufacture ofsemiconductor devices which are expected to be increasingly scaled down.

The upper layer film obtained from the composition to form the immersionupper layer film can prevent a photoresist film from contacting directlywith water, and not be deteriorated lithography performance of thephotoresist film due to permeation of water. Further, it can preventcontamination of the lens of the projection exposure device by thecomponent eluted from the photoresist film.

The resin of the immersion upper layer film composition according to theembodiment of the present invention can form a water-stable film duringirradiation and dissolve in a developer to form a resist pattern.

The term “a water-stable film during irradiation” used herein means thata change in the thickness measured by the water-stable evaluation methoddescribed later is 0.5% or less of the initial thickness. And the term“dissolve in a developer to form a resist pattern” means that there areno residues by naked eye observation and the upper layer film is removedon the resist pattern after development. Thus, the resin according tothe embodiment of the present invention is an alkali-soluble resin whichis scarcely soluble in water but is soluble in an alkaline aqueoussolution during development using the alkaline aqueous solution.

The alkali-soluble resin forming a water-stable film during irradiationand being dissolved in a subsequent developer contains recurring units.As the recurring units, a recurring unit having a carboxyl group, arecurring unit having a phenol site, and a recurring unit having afluorine atom-containing group on the side chain, in which the recurringunit having an alcoholic hydroxyl group on the side chain containing thefluoroalkyl group on at least the carbon atom of α-position ispreferable, can be given. The recurring units can be contained eitherindividually or in combinations of two or more.

As a radical polymerizable monomers forming the recurring unit having acarboxyl group, unsaturated monocarboxylic acids such as (meth)acrylicacid, crotonic acid, cinnamic acid, atropic acid,3-acetyloxy(meth)acrylic acid, 3-benzoyloxy (meth)acrylic acid,α-methoxy acrylic acid, and 3-cyclohexyl (meth)acrylic acid; unsaturatedpolycarboxylic acids such as fumaric acid, maleic acid, citraconic acid,mesaconic acid, and itaconic acid; monoesters such as monomethyl esterof the unsaturated monocarboxylic acid, monoethyl ester, mono n-propylester, and mono n-butyl ester;2-(meth)acrylamide-2-methylpropanecarboxylic acid,2-α-carboxyacrylamide-2-methylpropanecarboxylic acid,2-α-carboxymethylacrylamide-2-methylpropanecarboxylic acid,2-α-methoxycarbonylacrylamide-2-methylpropanecarboxylic acid,2-α-acetyloxyacrylamide-2-methylpropanecarboxylic acid,2-α-phenylacrylamide-2-methylpropanecarboxylic acid,2-α-benzylacrylamide-2-methylpropanecarboxylic acid,2-α-methoxyacrylamide-2-methylpropanecarboxylic acid,2-α-cyclohexylacrylamide-2-methylpropanecarboxylic acid,2-α-cyanoacrylamide-2-methylpropanecarboxylic acid, and the like can begiven.

Of these monomers, (meth) acrylic acid and crotonic acid are preferable.

As a radical polymerizable monomers forming the recurring unit having aphenolic site, hydroxystyrene derivatives such as p-hydroxystyrene,m-hydroxystyrene, o-hydroxystyrene, α-methyl-p-hydroxystyrene,α-methyl-m-hydroxystyrene, α-methyl-o-hydroxystyrene, 2-allylphenol,4-allylphenol, 2-allyl-6-methylphenol, 2-allyl-6-methoxyphenol,4-allyl-2-methoxyphenol, 4-allyl-2,6-dimethoxyphenol, and4-allyloxy-2-hydroxybenzophenone; hydroxystyrene (meth)acrylamidederivatives such as 4-hydroxyphenyl (meth)acrylamide,4-hydroxy-3,5-dimethyl (meth)acrylamide, 2-hydroxyphenyl(meth)acrylamide, 2-hydroxy-3-methylphenyl (meth)acrylamide,2-hydroxy-5-methylphenyl (meth)acrylamide, 2-hydroxy-3,5-dimethylphenyl(meth)acrylamide, 4-hydroxy-cyclohexyl (meth)acrylamide,2-hydroxy-cyclohexyl (meth)acrylamide, and the like can be given.

Of these monomers, p-hydroxystyrene, α-methylhydroxystyrene and4-hydroxyphenyl (meth)acrylamide are preferable.

As the recurring unit having a fluorine atom-containing group on theside chain, the recurring unit having an alcoholic hydroxyl group on theside chain containing a fluoroalkyl group on at least the carbon atom ofα-position is particularly preferable.

As the fluoroalkyl group in the recurring unit having an alcoholichydroxyl group on the side chain containing a fluoroalkyl group on atleast the carbon atom of α-position, a trifluoromethyl group ispreferable. When the recurring unit contains at least one fluoroalkylgroup on the α-position, a hydrogen atom of the alcoholic hydroxyl grouptends to be left by electron withdrawing of the fluoroalkyl group andpresents acidity in the aqueous solution, whereby it becomes insolublein pure water but becomes alkali-soluble. As the example of therecurring unit, the recurring unit of the formula (1) can be given.

In the formula (1), R¹ represents a hydrogen atom or a methyl group, andit can be used both of them.

R² of the formula (1) represents an organic group and preferably adivalent hydrocarbon group. As the divalent hydrocarbon group, linear orcyclic hydrocarbon group are preferable.

As a preferable example of the R², methylene group, ethylene group,propylene groups such as 1,3-propylene group and 1,2-propylene group;saturated linear hydrocarbon groups such as tetramethylene group,pentamethylene group, hexamethylene group, heptamethylene group,octamethylene group, nonamethylene group, decamethylene group,undecamethylene group, dodecamethylene group, tridecamethylene group,tetradecamethylene group, pentadecamethylene group, hexadecamethylenegroup, heptadecamethylene group, octadecamethylene group,nonadecamethylene group, icosa methylene group, 1-methyl-1,3-propylenegroup, 2-methyl-1,3-propylene group, 2-methyl-1,2-propylene group,1-methyl-1,4-butylene group, 2-methyl-1,4-butylene group, methylidenegroup, ethylidene group, and propylidene group; monocyclic hydrocarboncyclic groups such as cycloalkylene groups having 3-10 carbon atoms suchas 1,3-cyclobutylene group, cyclopentylene groups such as1,3-cyclopentylene group, cyclohexylene groups such as 1,4-cyclohexylenegroup, cyclooctylene groups such as 1,5-cyclooctylene group;cross-linking cyclichydrocarbon cyclic groups such as hydrocarbon cyclicgroups having 2 to 4 carbocycles and 4-30 cyclic carbon atoms such asnorbornylene groups such as 1,4-norbornylene group and 2,5-norbornylenegroup, adamantylene groups such as 1,5-adamantylene group and2,6-adamantylene group; and the like can be given.

In particular, when an alicyclic hydrocarbon group is contained as R²,it is preferable to insert an alkylene group having 1-4 carbon atoms asspacer between a bistrifluoromethyl-hydroxy-methyl group and thealicyclic hydrocarbon group.

As examples of the formula (1), preferable R² is a hydrocarbon grouphaving 2,5-norbornylene group or 1,2-propylene group. As preferableexamples of the radical polymerizable monomers of the above formula (1),following formulas (M-1) to (M-3) can be given.

As the recurring unit having a fluorine atom-containing group on theside chain other than the recurring unit having an alcoholic hydroxylgroup on the side chain, a recurring unit having a fluoroalkyl group onthe side chain is preferable. The recurring unit can be obtained bycopolymerizing fluoroalkyl (meth)acrylate. The recurring unit is addedin order to control the refractive index of the upper layer film.

As the preferable example of a fluoroalkyl (meth)acrylate monomers,fluoroalkyl (meth)acrylates containing fluoroalkyl group having 1-20carbon atoms such as difluoromethyl (meth)acrylate, perfluoromethyl(meth)acrylate, 2,2-difluoroethyl (meth) acrylate, 2,2,2-trifluoroethyl(meth)acrylate, perfluoroethyl (meth)acrylate, 1-(perfluoromethyl)ethyl(meth)acrylate, 2-(perfluoromethyl)ethyl (meth)acrylate,2,2,3,3-tetrafluoropropyl (meth)acrylate, perfluoroethylmethyl(meth)acrylate, di(perfluoromethyl)methyl (meth)acrylate,perfluoropropyl (meth)acrylate, 1-methyl-2,2,3,3-tetrafluoropropyl(meth)acrylate, 1-(perfluoroethyl)ethyl (meth)acrylate,2-(perfluoroethyl)ethyl (meth) acrylate, 2,2,3,3,4,4-hexafluorobutyl(meth)acrylate, perfluoropropylmethyl (meth)acrylate, perfluorobutyl(meth)acrylate, 1,1-dimethyl-2,2,3,3-tetrafluoropropyl (meth)acrylate,1,1-dimethyl-2,2,3,3,3-pentafluoropropyl (meth)acrylate,2-(perfluoropropyl)ethyl (meth) acrylate,2,2,3,3,4,4,5,5-octafluoropentyl (meth)acrylate, perfluorobutylmethyl(meth) acrylate, perfluoropentyl (meth)acrylate,1,1-dimethyl-2,2,3,3,4,4-hexafluorobutyl (meth) acrylate,1,1-dimethyl-2,2,3,3,4,4,4-heptafluorobutyl (meth)acrylate,2-(perfluorobutyl)ethyl (meth)acrylate,2,2,3,3,4,4,5,5,6,6-decafluorohexyl (meth)acrylate,perfluoropentylmethyl (meth)acrylate, perfluorohexyl (meth)acrylate,1,1-dimethyl-2,2,3,3,4,4,5,5-octafluoropentyl (meth)acrylate,1,1-dimethyl-2,2,3,3,4,4,5,5,5-nonafluoropentyl (meth)acrylate,2-(perfluoropentyl)ethyl (meth)acrylate,2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoroheptyl (meth) acrylate,perfluorohexylmethyl (meth)acrylate, perfluoroheptyl (meth)acrylate,2-(perfluorohexyl)ethyl (meth)acrylate,2,2,3,3,4,4,5,5,6,6,7,7,8,8-tetradecafluorooctyl (meth) acrylate,perfluoroheptylmethyl (meth)acrylate, perfluorooctyl (meth)acrylate,2-(perfluoroheptyl)ethyl (meth)acrylate,2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9-hexadecafluorononyl (meth)acrylate,perfluorooctylmethyl (meth)acrylate, perfluorononyl (meth)acrylate,2-(perfluorooctyl)ethyl (meth)acrylate,2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10-octadecafluorodecyl(meth)acrylate, perfluorononylmethyl (meth)acrylate, perfluorodecyl(meth)acrylate, 2,2,3,3,4,4,4-hexafluorobutyl (meth)acrylate,2,2,3,3,4,4,4-heptafluorobutyl (meth)acrylate,3,3,4,4,5,5,6,6,6-nonafluorohexyl (meth)acrylate, and3,3,4,4,5,5,6,6,7,7,8,8,8-tridodecafluorooctyl (meth)acrylate;(2,2,2-trifluoroethyl) α-carboxyacrylate, (perfluoroethylmethyl)α-carboxyacrylate, (2,2,2-trifluoroethyl) α-carboxymethylacrylate,(perfluoroethylmethyl) α-carboxymethylacrylate, (2,2,2-trifluoroethyl)α-methoxycarbonylacrylate, (perfluoroethylmethyl)α-methoxycarbonylacrylate, (2,2,2-trifluoroethyl) α-acetyloxyacrylate,(perfluoroethylmethyl) α-acetyloxyacrylate, (2,2,2-trifluoroethyl)α-phenylacrylate, (perfluoroethylmethyl) α-phenylacrylate,(2,2,2-trifluoroethyl) α-benzylacrylate, (perfluoroethylmethyl)α-benzylacrylate, (2,2,2-trifluoroethyl) α-ethoxyacrylate,(perfluoroethylmethyl) α-ethoxyacrylate, (2,2,2-trifluoroethyl)α-2-methoxyethylacrylate, (perfluoroethylmethyl)α-2-methoxyethylacrylate, (2,2,2-trifluoroethyl) α-cyclohexylacrylate,(perfluoroethylmethyl) α-cyclohexylacrylate, (2,2,2-trifluoroethyl)α-cyanoacrylate, (perfluoroethylmethyl) α-cyanoacrylate,3[4[1-trifluoromethyl-2,2-bis[bis(trifluoromethyl)fluoromethyl]ethinyloxy]benzoyloxy]2-hydroxypropyl(meth)acrylate, (2,2,3,3,3-pentafluoropropyl) 2-phenylacrylate,(2,2,3,3,3-pentafluoropropyl) 2-benzylacrylate,(2,2,3,3,3-pentafluoropropyl) 2-ethoxyacrylate,(2,2,3,3,3-pentafluoropropyl) 2-cyclohexylacrylate,(2,2,3,3,3-pentafluoropropyl) 2-cyanoacrylate, and the like can begiven. These fluoroalkyl group-containing monomers can be used eitherindividually or in combination of two or more.

As the fluoroalkyl group-containing monomers of the embodiment of thepresent invention, fluoroalkyl (meth)acrylates having fluoroalkyl groupconsisting of 1-20 carbon atoms is preferable. Of these, perfluoroalkyl(meth)acrylate and fluoroalkyl (meth)acrylates in which a perfluoroalkylgroup is bonded to an ester oxygen atom through a methylene group, anethylene group, or a sulfonylamino group are more preferable.

It is preferable to copolymerize other radical polymerizable monomers tothe alkali-soluble resin of the embodiment of the present invention inorder to control, for example, the molecular weight, glass transitionpoint of the resin. The term “other” used herein refers to radicalpolymerizable monomers other than the above-mentioned radicalpolymerizable monomers. And acid-labile group-containing monomers can becopolymerized.

As the other radical polymerizable monomers or acid-labilegroup-containing monomers, (meth)acrylic alkyl esters, (meth)acrylicaryl esters, dicarboxylic acid esters, nitrile group-containing radicalpolymerizable monomers, amide bond-containing radical polymerizablemonomers, aliphatic vinyls, chlorine-containing radical polymerizablemonomers, conjugated diolefin, hydroxyl group-containing (meth)acrylicalkyl esters, and the like can be given. As examples of the monomers,(meth)acrylic alkyl esters such as methyl (meth)acrylate, ethyl(meth)acrylate, n-butyl (meth)acrylate, sec-butyl (meth)acrylate,tert-butyl (meth)acrylate, isopropyl (meth)acrylate, n-hexyl(meth)acrylate, cyclohexyl (meth) acrylate, 2-methylcyclohexyl(meth)acrylate, dicyclopentanyloxyethyl (meth)acrylate, isobornyl(meth)acrylate, dicyclopentanyl (meth)acrylate, methoxy dipropyleneglycol (meth)acrylate, butoxy dipropylene glycol (meth)acrylate, methoxyethylene glycol (meth) acrylate, methoxy propylene glycol(meth)acrylate, 2-methyl-2-adamantyl (meth)acrylate, 2-ethyl-2-adamantyl(meth)acrylate, 2-propyl-2-adamantyl (meth)acrylate, 2-butyl-2-adamantyl(meth)acrylate, 1-methyl-1-cyclohexyl (meth)acrylate,1-ethyl-1-cyclohexyl (meth)acrylate, 1-propyl-1-cyclohexyl(meth)acrylate, 1-butyl-1-cyclohexyl (meth)acrylate,1-methyl-1-cyclopentyl (meth)acrylate, 1-ethyl-1-cyclopentyl(meth)acrylate, 1-propyl-1-cyclopentyl (meth)acrylate,1-butyl-1-cyclopentyl (meth)acrylate, 1-adamantyl-1-methylethyl(meth)acrylate, and 1-bicyclo[2.2.2]heptyl-1-methylethyl (meth)acrylate;dicarboxylic acid esters such as diethyl maleate, diethyl fumarate, anddiethyl itaconate; (meth)acrylic aryl esters such as phenyl(meth)acrylate, benzyl (meth)acrylate; aromatic vinyls such as styrene,α-methylstyrene, m-methylstyrene, p-methylstyrene, vinyl toluene, andp-methoxystyrene; nitrile group-containing radical polymerizablemonomers such as acrylonitrile and methacrylonitrile; amidebond-containing radical polymerizable monomers such as acrylamide,methacrylamide, and trifluoromethanesulfonyl aminoethyl (meth) acrylate;aliphatic vinyls such as vinyl acetate; chlorine-containing radicalpolymerizable monomers such as vinyl chloride and vinylidene chloride;conjugated diolefins such as 1,3-butadiene, isoprene, and1,4-dimethylbutadiene can be given.

As examples of the hydroxyl group-containing (meth)acrylic alkyl esters,2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate,2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth)acrylate,2,3-dihydroxypropyl (meth)acrylate, polypropylene glycol (meth)acrylate,2-hydroxycyclohexyl (meth)acrylate, 4-hydroxycyclohexyl (meth)acrylate,3-hydroxy-1-adamantyl (meth)acrylate, 3,5-dihydroxy-1-adamantyl(meth)acrylate, and the like can be given. Of these, 2-hydroxyethyl(meth) acrylate and 3-hydroxy-1-adamantyl (meth)acrylate are preferable.

These monomers can be used either individually or in combination of twoor more.

It is preferable that an alkali-soluble resin according to theembodiment of the present invention is a resin containing a recurringunit having fluorine atoms-containing group on the side chain.

As the recurring unit having fluorine atoms-containing group on the sidechain, a recurring unit having an alcoholic hydroxyl group on the sidechain containing a fluoroalkyl group on at least the carbon atom ofα-position and/or a recurring unit having a fluoroalkyl group on theside chain are preferable. In particular, the alkali-soluble resincontaining a recurring unit having an alcoholic hydroxyl group on theside chain containing a fluoroalkyl group on at least the carbon atom ofα-position is preferable.

When the resin contains the recurring unit having a fluoroalkyl group onthe side chain independently, it is preferable that an acid-labilegroup-containing recurring unit is contained as resin component. It isalso preferable that an acid-labile group-containing recurring unit iscontained as resin component when a recurring unit having a group iscontained no fluorine atoms on the side chain. Since the recurring unitcontains the acid-labile group, the resin being dissolved in a developerafter irradiation can be obtained.

When the resin contains the recurring unit having an alcoholic hydroxylgroup on the side chain containing a fluoroalkyl group on at least thecarbon atom of α-position as the alkali-soluble resin component, theamount of the component is preferably 10 wt % or more, more preferably20 wt % or more, and particularly preferably 30 wt %. If the amount ofthe component is less than 10 wt %, the solubility in an alkalinesolution as a developer may be decreased. Thus, the upper layer film maynot be removed, and the residues are remained on the resist patternafter development.

When the resin contains the recurring unit having a fluoroalkyl group onthe side chain as the alkali-soluble resin component, the amount of thecomponent is 90 wt % or less. If the amount of the component exceeds 90wt %, the solubility in a monovalent alcohol having 6 or less carbonatoms may be significantly decreased and can not be prepared as theupper layer film composition. Or, the solubility in an alkaline solutionas a developer may be decreased, and may not be completely removed theupper layer film after development. Both of the defects may occur at thesame time.

When the resin contains the recurring unit having a carboxyl group asthe alkali-soluble resin component, the content of the carboxyl group isusually 3 wt % to 50 wt %, preferably 3 wt % to 40 wt %, andparticularly preferably 3 wt % to 30 wt %. If the content is less than 3wt %, the solubility in an alkaline solution as a developer may bedecreased. Thus, the upper layer film may not be removed, and theresidues are remained on the resist pattern after development. If thecontent of the recurring unit is more than 50 wt %, the stability towater during immersion exposure may be decreased, and the contents maybe eluted into water and contaminated the lens of the projection opticalsystem.

When the resin does not contain the recurring unit having a carboxylgroup as the alkali-soluble resin component, the total content of therecurring unit having a phenol site and the recurring unit having analcoholic hydroxyl group on the side chain containing a fluoroalkylgroup on the carbon atom of α-position is usually 20 wt % or more,preferably 30 wt % or more, and particularly preferably 40 wt % or more.If the content of the recurring unit is less than 20 wt %, thesolubility in an alkaline solution as a developer may be decreased.Thus, the upper layer film may not be removed, and the residues areremained on the resist pattern after development. If the content of therecurring unit is excessively, the stability to water during immersionexposure may be decreased, and the contents may be eluted into water andcontaminated the lens of the projection optical system.

The radical polymerizable monomers having a carboxyl group on the sidechain or having a phenol site can copolymerize to the alkali-solubleresin in order to control the solubility in the developer.

It is preferable that the amount of the units derived from the radicalpolymerizable monomers having a phenol site be less than 20 wt %,because the site has a large absorption of light at a wavelength of 193nm when using for ArF exposure.

The amount of the units derived from the other radical polymerizablemonomers or the acid-labile group-containing monomers; (1) when theresin contains the recurring unit having a carboxyl group as thealkali-soluble resin component, the content of the units are usually 20wt % or more, preferably 30 wt % or more, and particularly preferably 40wt % or more; (2) when the resin does not contain the recurring unithaving a carboxyl group as the alkali-soluble resin component, thecontent of the units are usually 80 wt % or less, preferably 70 wt % orless, and particularly preferably 60 wt % or less.

As the polymerization solvent used in the preparation for alkali-solubleresin, alcohols such as methanol, ethanol, 1-propanol, 2-propanol,1-butanol, 2-butanol, ethylene glycol, diethylene glycol, and propyleneglycol; cyclic ethers such as tetrahydrofuran and dioxane; alkyl ethersof polyhydric alcohols such as ethylene glycol monomethyl ether,ethylene glycol monoethyl ether, ethylene glycol dimethyl ether,ethylene glycol diethyl ether, diethylene glycol monomethyl ether,diethylene glycol monoethyl ether, diethylene glycol dimethyl ether,diethylene glycol diethyl ether, diethylene glycol ethylmethyl ether,propylene glycol monomethyl ether, and propylene glycol monoethyl ether;alkyl ether acetates of polyhydric alcohol such as ethylene glycol ethylether acetate, diethylene glycol ethyl ether acetate, propylene glycolethyl ether acetate, and propylene glycol monomethyl ether acetate;aromatic hydrocarbons such as toluene and xylene; ketones such asacetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone,4-hydroxy-4-methyl-2-pentanone, and diacetone alcohol; esters such asethyl acetate, butyl acetate, ethyl 2-hydroxypropionate, ethyl2-hydroxy-2-methylpropionate, ethyl ethoxyacetate, ethyl hydroxyacetate,methyl 2-hydroxy-3-methylbutanoate, methyl 3-methoxypropionate, ethyl3-methoxypropionate, ethyl 3-ethoxypropionate, and methyl3-ethoxypropionate, and the like can be given. Of these, cyclic ethers,alkyl ethers of polyhydric alcohol, alkyl ether acetates of polyhydricalcohol, ketones, and esters are preferable.

As the solvent for the radical copolymerization, an appropriate radicalpolymerization initiator can be used. As examples of the solvents, azocompounds such as 2,2′-azobisisobutyronitrile, 2,2′-azobis(methyl2-methylpropionate), 2,2′-azobis(2,4-dimethylvaleronitrile),2,2′-azobis(4-methoxy-2-dimethylvaleronitrile); organic peroxides suchas benzoyl peroxide, lauroyl peroxide, tert-butylperoxy pivalate, and1,1′-bis(tert-butylperoxy)cyclohexane, and also hydrogen peroxide. Inthe case of using peroxide as a radical polymerization initiator, thismay be combined with a reducing agent so as to form a redox-typeinitiator.

A polystyrene-reduced weight average molecular weight (hereinafterreferred to as “Mw”) of the alkali-soluble resin obtained by the abovemanner determined by gel permeation chromatography (GPC) is 2,000 to100,000, preferably 2,500 to 50,000, and still more preferably 3,000 to20,000. If the Mw of the alkali-soluble resin is less than 2,000, waterresistance as an upper layer film and mechanical properties may besignificantly decreased. If the Mw exceeds 100,000, solubility insolvent described later may be significantly decreased. The ratio of Mwto the polystyrene-reduced number molecular weight (hereinafter referredto as “Mn”) determined by gel permeation chromatography (GPC) (Mw/Mn) ofthe resin is usually 1-5, and preferably 1-3.

It is preferable that the resin have a low content of the impuritiessuch as halogen, metal, and the like. As a result, it may be furtherimproved the applicability as the upper layer film and the uniformsolubility in an alkaline developer. As a method of the purificationmethod for the resin, for example, washing with water or a chemicalpurification method such as a liquid-liquid extraction and the like canbe given. Moreover, the chemical purification method can use thecombination of a physical purification method ultrafiltration method,centrifugation, and the like. In the embodiment of the presentinvention, the resins can be used either individually or in combinationsof two or more.

As solvents for the immersion upper layer film composition according tothe embodiment of the present invention, the solvents that can dissolvethe alkali-soluble resin, and dose not deteriorate lithographyperformance during applying to the photoresist film with beingintermixed with the photoresist film, can be used.

As the solvent, a solvent containing a monovalent alcohol having 6 orless carbon atoms can be given. As examples of the solvents, methanol,ethanol, 1-propanol, isopropanol, n-propanol, 1-butanol, 2-butanol,2-methyl-2-propanol, 1-pentanol, 2-pentanol, 3-pentanol, n-hexanol,cyclohexanol, 2-methyl-2-butanol, 3-methyl-2-butanol,2-methyl-1-butanol, 3-methyl-1-butanol, 2-methyl-1-pentanol,2-methyl-2-pentanol, 2-methyl-3-pentanol, 3-methyl-1-pentanol,3-methyl-2-pentanol, 3-methyl-3-pentanol, 4-methyl-1-pentanol,4-methyl-2-pentanol, and the like can be given. Of these, ethanol andisopropanol are preferable, and isopropanol is particularly preferable.These monovalent alcohols having 6 or less carbon atoms can be usedeither individually or in combination of two or more.

In terms of safety grounds especially boiling point or flash point,2-propanol, 1-butanol, 2-butanol, 2-methyl-2-pentanol,3-methyl-2-pentanol, and 4-methyl-2-pentanol are preferable.

Other solvents may be appropriately added to the alkali-soluble resincomposition in order to control the applicability when applying theupper layer film to the photoresist film. The other solvents can beuniformly applied the upper layer film without being eroded thephotoresist film.

As the other solvent, polyhydric alcohols such as ethylene glycol andpropylene glycol; cyclic ethers such as tetrahydrofuran and dioxane;alkyl ethers of polyhydric alcohol such as ethylene glycol monomethylether, ethylene glycol monoethyl ether, ethylene glycol dimethyl ether,ethylene glycol diethyl ether, diethylene glycol monomethyl ether,diethylene glycol monoethyl ether, diethylene glycol dimethyl ether,diethylene glycol diethyl ether, diethylene glycol ethylmethyl ether,propylene glycol monomethyl ether, and propylene glycol monoethyl ether;alkyl ether acetates of polyhydric alcohol such as ethylene glycol ethylether acetate, diethylene glycol ethyl ether acetate, propylene glycolethyl ether acetate, and propylene glycol monomethyl ether acetate;aromatic hydrocarbons such as toluene and xylene; ketones such asacetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone,4-hydroxy-4-methyl-2-pentanone, and diacetone alcohol; esters such asethyl acetate, butyl acetate, ethyl 2-hydroxypropionate, ethyl2-hydroxy-2-methylpropionate, ethyl ethoxyacetate, ethyl hydroxyacetate,methyl 2-hydroxy-3-methylbutanoate, methyl 3-methoxypropionate, ethyl3-methoxypropionate, ethyl 3-ethoxypropionate, and methyl3-ethoxypropionate; and water can be given. Of these, cyclic ethers,alkyl ethers of polyhydric alcohol, alkyl ether acetates of polyhydricalcohol, ketones, esters, and water are preferable.

The amount of the other solvent is 30 wt % or less, preferably 20 wt %or less in the solvent component. If the amount of the other solventexceeds 30 wt %, the other solvent erodes the photoresist film, occursthe problem such as intermixing between the photoresist film and theupper layer film, thereby causing it significantly deteriorates theresolution of the photoresist.

Surfactants exhibiting an action of improving the applicability,anti-foaming ability and levering ability may optionally be added to theimmersion upper layer film composition of the embodiment of the presentinvention.

As the surfactant, fluorochemical surfactant can be used. As examples ofthe surfactants, commercially available products such as BM-1000,BM-1100 (manufactured by BM Chemie Co.), MEGAFAC F142D, F172, F173, F183(manufactured by Dainippon Ink and Chemicals, Inc.), Fluorad FC-135,FC-170C, FC-430, FC-431 (manufactured by Sumitomo 3M Ltd.), SurflonS-112, S-113, S-131, S-141, S-145 (manufactured by Asahi Glass Co.,Ltd.), SH-28PA, SH-190, SH-193, SZ-6032, SF-8428 (manufactured by Torayand Dow Corning Corp.) can be given.

The amount of surfactants to be added is usually 5 parts by weight orless for 100 parts by weight of the alkali-soluble resin.

The method of forming photoresist pattern according to the embodiment ofthe present invention is described below.

A photoresist is applied to a substrate to form a photoresist film. Asthe substrate, a silicon wafer, an aluminum-coated wafer, or the likemay be used in the step of forming a photoresist film applied to asubstrate. In order to bring out the potential of the resist film, anorganic or inorganic antireflection film may be formed on the substrateas disclosed in JP-B-6-12452, for example.

The photoresist used is not particularly limited, and may beappropriately selected depending on the purpose of the resist. Asexamples of the resist, a positive-tone or negative-tonechemically-amplified resist containing an acid generator can be given.

When using the immersion upper layer film which formed by compositionaccording to the embodiment of the present invention, the positive-toneresist is preferable. In the chemically-amplified positive-tone resist,an acid-labile organic group in the polymer dissociates by the action ofan acid generated from the acid generator upon exposure to produce acarboxyl group, for example. As a result, the exposed portion of theresist exhibits increased solubility in an alkaline developer and isdissolved in and removed by an alkaline developer, whereby apositive-tone resist pattern is obtained.

The photoresist film is formed by dissolving a resin composition to formthe photoresist film in an appropriate solvent to a solid content of 0.1to 20 wt %, filtering the solution through a filter with a pore size ofabout 30 nm to obtain a resist solution, applying the resist solution toa substrate using an appropriate coating method such as rotationalcoating, cast coating, or roll coating, and prebaking (hereinafterabbreviated as “PB”) the applied resist solution to volatilize thesolvent. In this case, a commercially available resist solution may bedirectly used.

A step of forming the upper layer film using the immersion upper layerfilm composition is the step by applying the immersion upper layer filmcomposition of the embodiment of the present invention to thephotoresist film, and usually baking again to form the immersion upperlayer film of the embodiment of the present invention. In this step, theimmersion upper layer film is formed in order to protect the photoresistfilm and prevent contamination of the lens of the projection exposuredevice by the component eluted from the photoresist film.

A reflex inhibition effect at the interface on the resist film tends tobe increased by closing the thickness of the upper layer film toodd-numbered fold of λ/4m (λ: wavelength of radiation; m: refractiveindex of the upper layer film). Therefore, it is preferable to bring thethickness of the upper layer film closer to the value. In the embodimentof the present invention, one of the treatments of prebaking afterapplying the resist solution and baking after applying the upper layerfilm composition can be cut to simplify the steps.

A resist pattern is formed by applying radiation to the photoresist filmand the immersion upper layer film is formed using water as a mediumthrough a mask having a specific pattern, and developing the photoresistfilm. In this step, the photoresist film is subjected to immersionexposure, baked at a specific temperature, and developed.

Water filled between the photoresist film and the upper layer film canbe adjusted pH. In particular, pure water is preferable.

As the radiation used for immersion exposure, various types of radiationsuch as visible light; ultraviolet rays such as g-line and i-line; farultraviolet rays such as an excimer laser light; X-rays such assynchrotron radiation; and charged particle rays such as electron beamsmay be selectively used depending on the photoresist film used and thecombination of the photoresist film and the immersion upper layer film.In particular, it is preferable to use light from an ArF excimer laser(wavelength: 193 nm) or a KrF excimer laser (wavelength: 248 nm).

It is preferable to perform post exposure baking (hereinafterabbreviated as “PEB”) in order to provide the resist film with improvedresolution, pattern profile, developability, and the like. The bakingtemperature is usually about 30 to 200° C., and preferably 50 to 150°C., although the baking temperature is appropriately adjusted dependingon the resist used and the like.

The photoresist film is then developed using a developer and washed toform a desired resist pattern. In this case, the immersion upper layerfilm is not demanded to perform a removal treatment separately. The filmis removed completely by washing during or after development. That isone of important characteristic of the embodiment of the presentinvention.

As the alkaline developer when forming a resist pattern according to theembodiment of the present invention, an alkaline aqueous solutionprepared by dissolving sodium hydroxide, potassium hydroxide, sodiumcarbonate, sodium silicate, sodium metasilicate, ammonia, ethylamine,n-propylamine, diethylamine, di-n-propylamine, triethylamine,methydiethylamine, dimethylethanolamine, triethanolamine, tetramethylammonium hydroxide, tetraethyl ammonium hydroxide, pyrrole, piperidine,choline, 1,8-diazabicyclo[5.4.0]-7-undecene,1,5-diazabicyclo[4.3.0]-5-nonane, and the like. A water-soluble organicsolvent, for example alcohols such as methanol, ethanol or the like, ora surfactant may be appropriately added to the developer. When thephotoresist film is developed using the alkaline aqueous solution, thefilm is usually washed with water after development.

EXAMPLES Resin Synthesis Example 1

Resins (A-1) to (A-8) which form a water-stable film during irradiationand be dissolved in a developer after forming a resist pattern wereprepared using the following method. And comparative resin (A-32) wasprepared using the following method. The Mw and Mn of the resins (A-1)to (A-8) and comparative resin (A-32) were measured by gel permeationchromatography (GPC) using GPC columns (manufactured by Tosoh Corp.,G2000H_(XL)×2, G3000H_(XL)×1, G4000H_(XL)×1) under the followingconditions. Flow rate: 1.0 ml/minute, eluate: tetrahydrofuran, columntemperature: 40° C., standard reference material: monodispersedpolystyrene

As the monomer other than the monomers (M-1) to (M-3) given above,monomers (M-4) to (M-14) of the following formula are given.

A homogenous monomer solution was prepared by dissolving 50 g of themonomer (M-1), 5 g of the monomer (M-6), 25 g of the monomer (M-11), 20g of the monomer (M-12), and 6.00 g of 2,2′-azobis-(methyl 2-methylpropionate) in 200 g of methyl ethyl ketone. A 1,000 ml three-neck flaskcharged with 100 g of methyl ethyl ketone was purged with nitrogen gasfor 30 minutes. After purging with nitrogen, the contents of the flaskwere heated to 80° C. with stirring. The monomer solution prepared inadvance was added dropwise to the flask using a dripping funnel at arate of 10 ml per five minutes. The monomers were polymerized for fivehours after initiation of the addition (i.e. polymerization start time).After completion of polymerization, the reaction solution was cooled to30° C. or less and poured into 2,000 g of heptane, and the precipitatedwhite powder was separated by filtration.

The separated white powder was mixed with 400 g of heptane to prepare aslurry, and the slurry was stirred. After performing this operationtwice, the slurry was washed, separated by filtration, and dried at 50°C. for 17 hours to obtain a white powdery resin (A-1) (89 g; yield: 89wt %). The resin (A-1) had a molecular weight (Mw) of 7,300.

The resins ware prepared by the same manner shown the compositions inTable 1. The yield and Mw of each resin are shown in Table 1. The unitof the Table 1 is gram (g).

TABLE 1 Resin M-1 M-2 M-3 M-4 M-5 M-6 M-7 M-8 M-9 M-10 M-11 M-12 MwYield (%) A-1 50 — — — — 5 — — — — 25 20 7300 89 A-2 70 — — — — — — 20 —— 10 — 6800 88 A-3 — 40 — — 20 5 — — 35 — — — 6400 86 A-4 — 60 — — — —30 — — — 10 — 6800 86 A-5 — 80 — — — — — — — 10 10 — 7400 87 A-6 — — 60— — — — 10 20 — 10 — 7100 84 A-7 — — — — 50 20  30 — — — — — 7200 83 A-8— — — 70 10 — — — — — 20 — 6800 81 A-32 — — — — 50 — 10 — — — 40 — 790087

Resin Synthesis Example 2

Resins (A-9) to (A-31) were prepared in proportions (units; gram (g))shown in Table 2.

A monomer solution was prepared by dissolving monomers and initiators(2,2′-azobis-(methyl 2-methyl propionate)) shown in Table 2 in 200 g ofisopropanol. A 1,500 ml three-neck flask equipped with a thermometer anda dripping funnel was charged with 100 g of isopropanol, and purged withnitrogen gas for 30 minutes. After purging with nitrogen, the contentsof the flask were heated to 80° C. with stirring using magnetic stirrer.The monomer solution was then added to dropwise to the flask over threehours using a dripping funnel After completion of dropwise, the reactionwas further continued for another three hours. The solution was cooledto 30° C. or less and a polymer solution was obtained.

Post-treatment was conducted by the “post-treatment method (1)” and“post-treatment method (2)” of resins (A-9) to (A-18) and resins (A-19)to (A-31) respectively. Each method was carried out as follows.

Post-Treatment Method (1):

The polymer solution was added dropwise to 3,000 g of n-heptane over 20minutes using a dripping funnel with stirring. The polymer solution wasstirred for another one hour. The resulting slurry solution was thenfiltered using a Buchner funnel The separated white powder was added to600 g of n-heptane with stirring to prepared slurry solution, and againfiltered using a Buchner funnel The resulting powder was dried at 50° C.for 24 hours in the vacuum drier. Mw, Mw/Mn (dispersity of molecularweight) and yield (wt %) of the resulting powder were measured. Theresults are shown in Table 2.

Post-Treatment Method (2):

The polymer solution was concentrated until reduced by 200 g, pouredinto a separating funnel with 200 g of methanol and 1600 g of n-heptane,stirred sufficiently, and separated the liquid of lower layer. Theliquid of lower layer was added to 200 g of methanol and 1600 g ofn-heptane, and again separated the lower layer liquid using a separatingfunnel. The resulting lower layer liquid was carried out a solventsubstitution into 1-butanol or 4-methyl-2-pentanol. A solid content ofthe sample was calculated based on the weight of the residue which wasobtained by heating 0.3 g of the resin solution on the aluminum plateusing the hotplate at 140° C. for two hours. The calculated value wasused for the subsequent preparation of the upper layer film solution andcalculation of the yield. Mw, Mw/Mn (dispersity of molecular weight) andyield (wt %) of the resulting resin solution were measured. The resultsare shown in Table 2.

TABLE 2 Resin M-1 M-2 M-3 M-6 M-7 M-8 M-9 M-10 M-11 M-13 M-14 InitiatorMw Mw/Mn Yield(%) A-9 17.7 — — 12.7 69.6 — — — — — — 9.0 7800 2.30 95A-10 — 14.9 — 13.1 72.0 — — — — — — 9.3 6800 1.82 98 A-11 — — — 13.574.2 12.3 — — — — — 9.6 7500 1.88 93 A-12 — — — 13.6 74.8 — 11.6 — — — —9.7 6900 1.87 94 A-13 — — — 11.8 64.6 — — — — 23.6 — 8.4 7000 1.82 78A-14 — — —  9.4 34.3 — — — — 56.4 — 6.7 6600 1.55 70 A-15 — — — 13.373.2 — — — — — 13.5 9.5 7600 2.00 97 A-16 — 41.4 —  8.1 44.4 — — — 6.1 —— 8.6 7300 1.81 95 A-17 47.3 — — 11.3 41.4 — — — — — — 8.1 8200 2.00 80A-18 — — — 21.0 57.6 — 13.4 — 7.9 — — 11.2 7100 1.90 90 A-19 — 67.8 — —27.2 — — — 5.0 — — 7.1 8000 1.77 84 A-20 — — — 14.2 — — — — — 85.8 — 6.16500 1.85 70 A-21 — 83.3 — — 16.7 — — — — — — 6.5 8100 1.77 80 A-22 —65.1 — — 34.9 — — — — — — 6.8 8500 1.71 83 A-23 34.4 65.6 — — — — — — —— — 5.9 7800 1.94 81 A-24 — 88.3 — — — — 11.7 — — — — 6.5 6800 1.84 78A-25 — 87.7 — — — 12.3 — — — — — 6.5 6200 1.82 84 A-26 — 76.3 — — — — —— — 23.7 — 5.6 6300 1.69 76 A-27 — 50.6 — 14.8 — 34.5 — — — — — 9.1 72001.72 81 A-28 — 77.5 — — — 17.6 — — 4.9 — — 6.9 7700 1.90 85 A-29 — —73.6 — — 26.4 — — — — — 6.9 7800 1.81 79 A-30 — 88.9 — — — — — 11.1 — —— 6.5 6400 1.75 82 A-31 — 100.0  — — — — — — — — — 6.3 6700 1.81 86

Examples 1 to 47 and Comparative Examples 1 to 4

The immersion upper layer film composition was prepared by using theresins (A-1) to (A-32).

A solution was prepared by dissolving 1 g of the resin shown in Table 1and Table 2 in 99 g of the solvent shown in Table 3 with stirring fortwo hours. The solution was filtered through a membrane filter with apore size of 200 nm. In Table 2, IPA represents isopropanol; n-BuOHrepresents normal butanol; t-BuOH represents tertiary butanol; PGMErepresents propylene glycol monomethyl ether; PG represents propyleneglycol; MEK represents methyl ethyl ketone; 3M2P represents3-methyl-2-pentanol; and 4M2P represents 4-methyl-2-pentanol. In Table3, the ratio of the mixed-solvent refers to the ratio of weight.

Evaluation of the immersion upper layer film composition was carried outas follows. The results are shown in Table 3.

(1) Evaluation Method of Solubility

In the Example 1 to 28 and Comparative Examples 1 to 4, 1 g of the resinfor the upper layer film was dissolved in 99 g of solvent shown in Table3, and the mixture was stirred for three hours at rotational speed of100 rpm using Three-One Motor. When the mixture becameuniformly-dispersed, it was determined that the solubility was good(“Good”). When the mixture was caused undissolved matter or whiteturbidity, it was determined that the solubility was poor (“Bad”).

In the Example 29 to 47, necessary solvent requirements was added to theresin solution in the same manner as preparation of the evaluationsolution, and the mixture was stirred for three hours at rotationalspeed of 100 rpm using Three-One Motor. When the mixture becameuniformly-dispersed, it was determined that the solubility was good(“Good”). When the mixture was caused undissolved matter or whiteturbidity, it was determined that the solubility was poor (“Bad”).

(2) Evaluation Method of Removal Performance of Upper Layer Film

The upper layer film was applied to an eight-inch silicon wafer by spincoating in the Clean Track (“ACT-8”, manufactured by Tokyo ElectronLtd.). After performing PB (90° C., 60 sec), a coating film with athickness of 32 nm was formed. The thickness was measured using theLAMBDA ACE (“VM-90”, manufactured by Dainippon Screen MFG Co., LTD). Thecoating film was then subjected to puddle development (developercomponent: 2.38 wt % TMAH aqueous solution) using the CLEAN TRACK ACT8(60 sec), spin-dried, and wafer surface were observed. When the waferwas developed with no residues, it was determined that the removalperformance was good (“Good”). When the residues were observed, it wasdetermined that the removal performance was poor (“Bad”).

(3) Evaluation Method of Intermixing

The JSR ArF AR1221J was applied to a HMDS-treated (100° C., 60 sec)eight-inch silicon wafer by spin coating. The immersion upper layer filmcomposition was applied to the wafer by spin coating a PB (90° C., 60sec) to form a coating film with a thickness of 32 nm. Then, the waferwas discharged ultrapure water to the wafer using an rinse nozzle of theCLEAN TRACK ACT8 (60 sec), spin-dried at 4000 rpm for 15 seconds,subjected to puddle development using an LD nozzle of the CLEAN TRACKACT8 (60 sec), and removed the upper layer film. 2.38% of TMAH aqueoussolution was used as the developer in this development process. Theimmersion upper layer film was removed in the development process, butthe resist film was unexposed and remained on the wafer. The thicknesswas measured using the LAMBDA ACE (“VM-90”, manufactured by DainipponScreen MFG. Co., LTD) around the process. When the range of a change ofthe resist thickness was 0.5% or less, there was no intermixing betweenthe resist film and the immersion upper layer film (“Good”). When therange of a change of the resist thickness was 0.5% or more, it wasindicated as “Bad”.

(4) Water-Stable Evaluation of Immersion Upper Layer Film Composition(Water Resistance)

The immersion upper layer film composition was applied to an eight-inchsilicon wafer by spin coating. After performing PB (90° C., 60 sec), acoating film with a thickness of 30 nm was formed. The thickness wasmeasured using the LAMBDA ACE “VM-90”. The wafer of the above substratewas then discharged ultrapure water to the wafer using a rinse nozzle ofthe CLEAN TRACK ACT8 (60 sec), spin-dried at 4000 rpm for 15 seconds,and the thickness of the substrate was again measured. When the amountof decrease in the thickness was 0.5% or less of the initial thickness,it was determined that the coating film is stable (“Good”). When theamount of decrease in the thickness was 0.5% or more of the initialthickness, it was determined that the coating film is not stable(“Bad”).

(5) Patterning Evaluation

(5-1) Evaluation Method of Resist Pattern (ArF Exposure)

The evaluation method of resist patterning using the upper layer film isdescribed below.

A lower-layer anti-reflective film ARC29 (manufactured by BrewerScience) was applied to an eight-inch silicon wafer by spin coating a PB(90° C., 60 sec) to form a coating with a thickness of 77 nm. Then,patterning was performed by using JSR ArF AR1221J. The AR1221J wasapplied to the wafer by spin coating a PB (130° C., 90 sec) to form acoating film with a thickness of 205 nm. After performing PB, the upperlayer film was applied to the wafer by spin coating a PB (90° C., 60sec), a coating film with a thickness of 32 nm was formed. The wafer wasexposed (dose: 30 mJ/cm²) using an ArF projection exposure device S306C(manufactured by Nikon Corporation) under optical conditions of NA:0.78, sigma: 0.85, and 2/3Ann. The wafer was discharged ultrapure waterto the wafer using a rinse nozzle of the CLEAN TRACK ACT8 (60 sec), andspin-dried at 4000 rpm for 15 seconds. Then the wafer was subjected toPEB (130° C., 90 sec) using a CLEAN TRACK ACT8 hot plate, subjected topuddle development using an LD nozzle of the CLEAN TRACK ACT8 (60 sec),rinsed with ultrapure water, and spin-dried at 4000 rpm for 15 seconds.

The patterns of the substrates corresponding to the 90 nm line/90 nmspace mask pattern were observed using a scanning electron microscopeS-9360 (manufactured by Hitachi Instruments Service Co., Ltd.). A casewhere the resist had no pattern collapse, development residuescorresponding to the space and pattern waves, and an excellent resistpattern was obtained for the developed substrates was indicated as“Good”, and a case where an excellent pattern was not obtained wasindicated as “Bad”. “-” indicates that the pattern evaluation was notconducted.

(5-2) Evaluation Method of Resist Pattern (KrF Exposure)

The evaluation method of the pattern obtained by applying the upperlayer film of the embodiment of the present invention on the ArF resistand being exposed by KrF (wavelength: 248 nm) is described below.

A lower-layer anti-reflective film DUV42 (manufactured by NissanChemical Industries, Ltd.) was applied to an eight-inch silicon wafer byspin coating a PB (205° C., 60 sec) to form a coating with a thicknessof 60 nm. Then, patterning was performed by using JSR ArF AR1221J. TheAR1221J was applied to the wafer by spin coating a PB (130° C., 90 sec)to form a coating film with a thickness of 205 nm. After performing PB,the upper layer film was applied to the wafer by spin coating a PB (90°C., 60 sec), a coating film with a thickness of 40 nm was formed. Thewafer was exposed (dose: 100 mJ/cm²) using a KrF projection exposuredevice S203B (manufactured by Nikon Corporation) under opticalconditions of NA: 0.68, sigma: 0.75, and 2/3Ann. The wafer wasdischarged ultrapure water to the wafer using a rinse nozzle of theCLEAN TRACK ACT8 (60 sec), and spin-dried at 4000 rpm for 15 seconds.Then the wafer was subjected to PEB (130° C., 90 sec) using a CLEANTRACK ACT8 hot plate, subjected to puddle development using an LD nozzleof the CLEAN TRACK ACT8 (60 sec), rinsed with ultrapure water, andspin-dried at 4000 rpm for 15 seconds.

The patterns of the substrates corresponding to the 150 nm line/150 nmspace mask pattern were observed using a scanning electron microscopeS-9360 (manufactured by Hitachi Instruments Service Co., Ltd.). A casewhere the resist had no pattern collapse, development residuescorresponding to the space and pattern waves, and an excellent resistpattern was obtained for the developed substrates was indicated as“Good”, and a case where an excellent pattern was not obtained wasindicated as “Bad”. “-” indicates that the pattern evaluation was notconducted.

TABLE 3 Removal Water Patterning Resin Solvent Solubility performanceIntermixing resistance KrF ArF Example  1 A-1 IPA Good Good Good Good —Good  2 A-2 IPA Good Good Good Good — Good  3 A-2 n-BuOH Good Good GoodGood — Good  4 A-2 t-BuOH Good Good Good Good — Good  5 A-2 IPA/PGME =95/5 Good Good Good Good — Good  6 A-3 IPA Good Good Good Good — Good  7A-4 IPA Good Good Good Good — Good  8 A-5 IPA Good Good Good Good — Good 9 A-6 IPA Good Good Good Good — Good 10 A-6 n-BuOH Good Good Good Good— Good 11 A-6 IPA/PGME = 95/5 Good Good Good Good — Good 12 A-7 IPA GoodGood Good Good — Good 13 A-8 IPA Good Good Good Good Good — 14 A-1 4M2PGood Good Good Good — Good 15 A-1 3M2P Good Good Good Good — Good 16 A-9n-BuOH Good Good Good Good — Good 17 A-10 n-BuOH Good Good Good Good —Good 18 A-11 4M2P Good Good Good Good — Good 19 A-12 n-BuOH Good GoodGood Good — Good 20 A-13 n-BuOH Good Good Good Good — Good 21 A-13 4M2PGood Good Good Good — Good 22 A-14 n-BuOH Good Good Good Good — Good 23A-14 n-BuOH/4M2P = 30/70 Good Good Good Good — Good 24 A-15 n-BuOH GoodGood Good Good — Good 25 A-16 n-BuOH Good Good Good Good — Good 26 A-174M2P Good Good Good Good — Good 27 A-17 n-BuOH Good Good Good Good —Good 28 A-18 n-BuOH Good Good Good Good — Good 29 A-19 n-BuOH Good GoodGood Good — Good 30 A-19 n-BuOH/4M2P = 50/50 Good Good Good Good — Good31 A-20 n-BuOH Good Good Good Good — Good 32 A-21 n-BuOH Good Good GoodGood — Good 33 A-22 n-BuOH Good Good Good Good — Good 34 A-23 n-BuOHGood Good Good Good — Good 35 A-23 4M2P Good Good Good Good — Good 36A-24 4M2P Good Good Good Good — Good 37 A-24 n-BuOH Good Good Good Good— Good 38 A-25 n-BuOH Good Good Good Good — Good 39 A-25 4M2P Good GoodGood Good — Good 40 A-26 4M2P Good Good Good Good — Good 41 A-26n-BuOH/4M2P = 50/50 Good Good Good Good — Good 42 A-27 n-BuOH Good GoodGood Good — Good 43 A-28 n-BuOH Good Good Good Good — Good 44 A-29n-BuOH/4M2P = 50/50 Good Good Good Good — Good 45 A-30 n-BuOH Good GoodGood Good — Good 46 A-31 n-BuOH Good Good Good Good — Good 47 A-31n-BuOH/4M2P = 70/30 Good Good Good Good — Good Comparative Example  1A-1 PGME Good Good Bad Good — —  2 A-2 PG Good Good Good Bad — —  3 A-3MEK Good Good Bad Good — —  4 A-32 IPA Good Bad Good Good — —

The immersion upper layer film forming composition according to theembodiment is useful to form the upper layer film which protects aphotoresist and a lens of the projection exposure device without beingeluted the photoresist component during immersion exposure used for anessential technology for lithography.

Since the composition to form a immersion upper layer film of theembodiment of the present invention comprises a resin forming awater-stable film during irradiation and being dissolved in a subsequentdeveloper, and a solvent containing a monovalent alcohol having 6 orless carbon atoms, the composition protects a lens and a photoresistfilm during immersion exposure and can form a resist pattern exhibits anexcellent resolution, developability, and the like. The composition canbe suitably used in the field of microfabrication represented by themanufacture of semiconductor devices which are expected to become moreand more miniaturized in the future.

Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that within the scope of the appended claims, theinvention may be practiced otherwise than as specifically describedherein.

The invention claimed is:
 1. An immersion upper layer film compositioncomprising: an alkali-soluble resin capable of forming a water-stablefilm and capable of being dissolved in a developer, the alkali-solubleresin comprising: a first recurring unit comprising a recurring unitshown by a formula (1); and a second recurring unit comprising afluoroalkyl group on a side chain of the second recurring unit, andobtained by polymerizing fluoroalkyl (meth) acrylate; and a solvent todissolve the alkali-soluble resin,

wherein R¹ represents a hydrogen atom or a methyl group, and R²represents an organic group.
 2. The immersion upper layer filmcomposition according to claim 1, wherein the organic group representedby R² is a divalent hydrocarbon group.
 3. The immersion upper layer filmcomposition according to claim 2, wherein the divalent hydrocarbon groupconsists of an alkylene group having 1 to 4 carbon atoms and analicyclic hydrocarbon group, the alkylene group being located betweenthe alicyclic hydrocarbon group and thebistrifluoromethyl-hydroxy-methyl group in the formula (1).
 4. Theimmersion upper layer film composition according to claim 2, wherein thedivalent hydrocarbon group is a hydrocarbon group having a2,5-norbornylene group, or a 1,2-propylene group.
 5. The immersion upperlayer film composition according to claim 1, wherein an amount of thefirst recurring unit is 10 wt % or more with respect to a weight of thealkali-soluble resin.
 6. The immersion upper layer film compositionaccording to claim 1, wherein an amount of the second recurring unit is90 wt % or less with respect to a weight of the alkali-soluble resin. 7.A method of forming a photoresist pattern comprising: providing aphotoresist on a substrate to form a photoresist film; providing theimmersion upper layer film composition according to claim 1 on thephotoresist film to form an upper layer; exposing the photoresist filmand the upper layer with radiation through a predetermined mask patternand through water; and developing the photoresist film and the upperlayer to form a resist pattern, wherein the solvent included in theimmersion upper layer film composition is not intermixed with thephotoresist film.
 8. An immersion upper layer film compositioncomprising: an alkali-soluble resin capable of forming a water-stablefilm and capable of being dissolved in a developer, the alkali-solubleresin comprising: a recurring unit comprising a carboxyl group; and afluorine atom-containing recurring unit comprising a group whichcomprises a fluorine atom on a side chain of the fluorineatom-containing recurring unit, the fluorine atom-containing recurringunit comprising a second recurring unit comprising a fluoroalkyl groupon a side chain of the second recurring unit, and obtained bypolymerizing fluoroalkyl (meth) acrylate; and a solvent to dissolve thealkali-soluble resin.
 9. The immersion upper layer film compositionaccording to claim 8, wherein the fluorine atom-containing recurringunit comprises a first recurring unit comprising an alcoholic hydroxylgroup on a side chain of the first recurring unit, the alcoholichydroxyl group comprising a fluoroalkyl group on at least a carbon atomof α-position.
 10. The immersion upper layer film composition accordingto claim 9, wherein the first recurring unit comprises a recurring unitshown by a formula (1),

wherein R¹ represents a hydrogen atom or a methyl group, and R²represents an organic group.
 11. The immersion upper layer filmcomposition according to claim 10, wherein the organic group representedby R² is a divalent hydrocarbon group.
 12. The immersion upper layerfilm composition according to claim 11, wherein the divalent hydrocarbongroup consists of an alkylene group having 1 to 4 carbon atoms and analicyclic hydrocarbon group, the alkylene group being located betweenthe alicyclic hydrocarbon group and thebistrifluoromethyl-hydroxy-methyl group in the formula (1).
 13. Theimmersion upper layer film composition according to claim 11, whereinthe divalent hydrocarbon group is a hydrocarbon group having a2,5-norbornylene group, or a 1,2-propylene group.
 14. The immersionupper layer film composition according to claim 9, wherein an amount ofthe first recurring unit is 10 wt % or more with respect to a weight ofthe alkali-soluble resin.
 15. The immersion upper layer film compositionaccording to claim 8, wherein an amount of the second recurring unit is90 wt % or less with respect to a weight of the alkali-soluble resin.16. A method of forming a photoresist pattern comprising: providing aphotoresist on a substrate to form a photoresist film; providing theimmersion upper layer film composition according to claim 8 on thephotoresist film to form an upper layer; exposing the photoresist filmand the upper layer with radiation through a predetermined mask patternand through water; and developing the photoresist film and the upperlayer to form a resist pattern, wherein the solvent included in theimmersion upper layer film composition is not intermixed with thephotoresist film.